The long term goal of this research is to elucidate nerve cell communication and to study factors which exert influence on cell interactions such as those occurring during development (specific adhesion, chemotaxis) and alteration of synaptic function after axotomy and denervation. The study will elucidate the mechanisms of specificity and selective innervation. It is intended to study synaptic mechanism and nerve cell recognition and differentiation in autonomic vertebrate ganglia. The avian ciliary ganglia and its effector organs, a preparation developed by the principal investigator, will be used as an experimental model. The study will be done in embryonic as well as mature cells, and the experiments will be carried out in acutely isolated superfused preparations and in tissue and organ cultures of the same elements. The research will be centered on the pre- and postsynaptic contacts, the mutual interactions between these elements, and the modifications of these interactions by experimental manipulation of the central and peripheral connections. The physiological meaning of the dual, chemical and electrical mode of synaptic transmission will be studied, as well as the function of the presynaptic receptors in transmission, and the factors implied in the termination of transmitter action. Bibliographic references: Ultrastructural differences during embryonic cell death in normal and peripherally deprived ciliary ganglia. G. Pilar & L.Landmesser. 1975; Fate of ganglionic synapses and ganglion cell axons during normal and induced cell death. L. Landmesser & G. Pilar. 1975.